Hybrid Photonic-Plasmonic Cavity Design for Very Large Purcell Factors at Telecommunication Wavelengths

Hybrid photonic-plasmonic cavities can be tailored to display high Q factors and extremely small mode volumes simultaneously, which ultimately results in large values of the Purcell factor, FP. Amongst the different hybrid configurations, those based on a nanoparticle-on-a-mirror plasmonic cavity provide one of the lowest mode volumes, though so far their operation has been constrained to wavelengths below 1 Am. Here, we propose a hybrid configuration consisting of a silicon photonic crystal cavity with a slot at its center in which a gold nanoparticle is introduced. This hybrid system operates at telecom wavelengths and provides high Q-factor values (Q 105) and small normalized mode volumes (Vm 10-4), leading to extremely large Purcell-factor values, FP 107 - 108. The proposed cavity could be used in different applications such as molecular optomechanics, bio-and chemosensing, efficient quantum emitters, or enhanced Raman spectroscopy in the relevant telecom-wavelength regime.